Field
The disclosure relates generally to the field of navigation aid equipment, and more specifically to methods, apparatuses, and computer-readable media for providing integrity assurance of navigation aid equipment.
Background
Navigation aid systems provide relevant types of information to aircraft that may allow for safe and accurate aircraft positioning. To assure maximum safety, the radiated signal from navigation aid equipment is continuously monitored by a safety and/or integrity monitor. Navigation aid equipment that incorporates safety and/or integrity monitors include: Distance Measuring Equipment (DME), TACtical Air Navigation (TACAN), Very high frequency Omni-directional Range (VOR), Instrument Landing System (ILS), Marker Beacon (MB), and Non-Directional Beacons (NDB). Each navigation aid system has specific parameters that determine proper and safe performance.
DME systems are used to determine distance with respect to a DME ground station. A DME system may include an Ultra high frequency (UHF) transmitter/receiver in the aircraft (e.g., aircraft DME) and a UHF receiver/transmitter on the ground (e.g., DME ground station). The aircraft DME may determine position by transmitting a series of pulsed pairs to the ground-based DME and, after a predetermined time delay (e.g., 50 μsec), receive a reply from DME ground station that includes an identical sequence of pulsed pairs. Once the identical series of pulsed pairs is received, the aircraft DME may calculate the distance to the DME ground station.
In other words, the DME system provides a way for aircraft to calculate the physical distance to the DME ground station. The distance depends trigonometrically upon both the altitude of the aircraft above the DME ground station and the ground distance from the aircraft to the DME ground station.
DME systems are required to keep a certain degree of accuracy in accordance with international standards set by, for example, the Federal Aviation Administration (FAA), the European Aviation Safety Agency (EASA), the International Civil Aviation Organization (ICAO), etc. To ensure accuracy, flight inspection organizations periodically check critical parameters associated with DME ground stations to calibrate and certify precision of the DME system.
Some legacy navigation aid systems operate using outdated safety criteria. For example, some legacy systems are subject to failure mode, effects, and criticality analysis (FMECA) using a military standard (e.g., MIL-STD-1629) and a failsafe demonstration. However, advances in safety assurance methodology have resulted in newer safety assurance methods that are currently in use. The technologies used in legacy DME systems make it quite expensive to apply the newer safety criteria as safety assurance for such systems.
Therefore, there exists an unmet need in the art for methods, apparatuses, and computer-readable media that monitor the performance of navigation aid systems and reduce the expense of applying more newer safety criteria to legacy navigation aid systems.